1. Field of the Invention
The present invention relates to an image-taking apparatus having functions that automatically adjust parameters relating to image-taking (image acquiring).
2. Description of Related Art
Conventionally, the following functions that automatically adjust parameters relating to image-taking so as to take an excellent image are provided.
The autofocusing function automatically carries out focusing from a lens or a distance as a reference. In focusing, an error at a level that does not pose a problem in actual image-taking is allowed.
Furthermore, the auto exposure function is provided which automatically sets an amount of exposure for an image pickup element. Furthermore, the auto white balance adjusting function is also provided which automatically determines the color temperature of an acquired image and automatically adjusts the white balance.
Herein, regarding the focusing of the autofocusing function, in particular, in the case of a single lens reflex camera system, both the camera main body and image-taking lens have errors in manufacturing, for example, errors in the positions to which a focusing lens is driven in actuality in response to an input position instruction signal, or errors in the adjusted values, for example, errors in values for correction of a deviation between the results of calculation of the focusing lens position on the basis of the results of focus detection and the focusing lens position in the truly in-focus state. Therefore, in autofocusing in a case of a combination of a single lens reflex camera and an image-taking lens, a focus error exceeding the allowance value occurs.
Furthermore, in the auto exposure function, due to errors in the attaching position of a photometry element, adjusting errors in the auto exposure itself, and furthermore, due to errors caused by the combination with an image-taking lenses and differences in a user's preference, a difference appears between the auto exposure level set before shipment and the exposure level intended by a user. Furthermore, even in the auto white balance adjusting function, there is a gap between the color tone preferred by a user and the color tone automatically adjusted (corrected) by the camera.
Therefore, in Japanese Patent Application Laid-Open No. 2000-292684, a technique that solves the problem relating to the autofocusing function is proposed. In this technique, the position of the focusing lens calculated by a phase difference detection method is regarded as a first focus detection result, and a change in contrast of an image is detected while moving the focusing lens in a phased manner according to TV-AF or a method called a hill-climbing. AF, and a lens position where the contrast becomes highest is regarded as a second focus detection result. Then, the difference between the first and second focus detection results is stored as a correction value of autofocusing. During actual image-taking, the phase difference detection method and the abovementioned stored correction value are used to carry out autofocusing. Thereby, autofocusing with high accuracy can be carried out.
In addition, in Japanese Patent Application Laid-Open No. 2001-257933, as a technique that copes with differences in a user's preference with respect to the auto exposure function and the auto white balance adjusting function, a technique is proposed in which values obtained by correcting automatic functions by a user when taking images are defined as custom set values, and a plurality of combinations of these are stored in the camera. Thereby, the user can select custom set values corresponding to user's preference in the next image-taking.
However, in the technique proposed in Japanese Patent Application Laid-Open No. 2000-292684, focus detection must be carried out by a method (contrast detection method) other than the focus detection method used for actual image-taking. Calculation and control of the lens in the contrast detection method is extremely complicated, so that the capacity of the necessary calculation program and the lens control program becomes large. Therefore, the capacity of the memory that stores the programs must be increased or the capacity of the operation programs used for normal image-taking must be limited. Furthermore, electrical circuitry (low pass filter, etc., for extracting high frequency components from the output of the image pickup element) according to the contract detection method also becomes necessary.
Furthermore, the technique proposed in Japanese Patent Application Laid-Open No. 2001-257933 enables image acquiring adapted to a user's preference, however, it does not serve as a function that automatically corrects variations in manufacturing errors in each of the camera and the image-taking lens, and errors caused by the combination of the camera and the lens.